The present invention relates generally to electrical contactors. More specifically, the present invention relates to magnetic latching contactors that use electrical current pulses to change switching positions.
Electrical contactors and relays are commonly used for switching relatively large amounts of electrical current using relatively low current switching signals. An electrical contactor typically has electrical switching contacts for closing and opening an electrical circuit connected to the contactor. An electromechanical device is typically utilized to move the electrical switching contacts into and out of physical contact, thereby closing and opening the electrical circuit, respectively. The operation of the electromechanical device, in turn, is typically controlled by a relatively low current switching signal.
Many contactors have one passive stable switching position and one unstable active switching position. The stable switching position is passively maintained in the absence of externally provided active energy. For instance, a simple spring is often used to bias the electrical contacts into a first switching position, which will then be passively maintained. When a change in switching position is desired, an electrical switching signal is provided to the contactor, which in turn induces an active switching force on the electrical contacts. The active switching force moves the contacts into a second switching position, which is maintained until the electrical switching signal is removed from the contactor. A significant drawback to contactors with only one stable switching position is that energy must continually be supplied to the contactor to maintain the unstable switching position. This inefficient use of energy results in higher operational costs and also introduces heating problems into the contactor use and design.
To address these problems and others, contactors have been designed which provide multiple stable switching positions. Various arrangements and types of switching elements, electrical coils, springs, permanent magnets and mechanical latching mechanisms have been proposed to provide contactors with multiple stable switching positions.
While contactors with multiple stable switching positions have performed satisfactorily, those working in this art have recognized that important design improvements are needed. These include contactor reliability, particularly in high current switching applications where safety is of primary concern. One drawback of present contactors using mechanical latching mechanisms is that the latching mechanisms tend to wear out over time. To avoid the unreliability of mechanical latching mechanisms, some contactor designs utilize permanent magnets for latching. However, the permanent magnets are often placed in positions exposing them to mechanical stress and shock. The permanent magnets themselves then become potential failure points. Manufacturability is another important concern since it is closely related to product cost and quality. Typical contactor designs providing two stable switching positions involve a high number of piece-parts in manufacturably undesirable configurations. Also contactors have been designed to operate over a particular electrical current range, and these designs are not necessarily readily extendible to a contactor designed to operate over a different current range.
Hence, a longstanding need has existed for an improved electrical contactor that has multiple stable switching positions and that is cost effective, reliable, manufacturable and extendible to a variety of electrical current ranges.